Microwave duplex switch



y 5, 1959 J? F. ZALESKl 2,885,677

MICROWAVE DUPLEX SWITCH Filed July 7, 1955 ATTOIQIVEY 2 Sheets-Sheet l I y 1959 J. F. ZALESKI 2,885,677

MICROWAVE DUPLEX SWITCH Filed July 7, 1955 2 Sheets$heet 2 INVENTOR. JO/IA/ F. 24L 56K! ,47' TOENE' Y MICROWAVE DUPLEX SWITCH. I

John F. Zaleski, Valhalla, N.Y., assignor to General The cisiti? Laboratory Incorporated, a corporation of New Yor Application July 7, 1955,.Serial No. 520,506-

3 Claims. (Cl. 343-777) This invention relates to a combined microwave duplexer and microwave switch. More specifically the invention relates to a microwave field rotator of the magnetically energized type which provides duplex operation and reverses the phase of the output.

The invention provides a microwave 'guide structure having a generator arm and a receiver arm at one endand a pair of load arms at the other end. The structure contains a microwave field rotator capable of rotating the microwave field in the Faraday magneto-optical sense under the influence of a reversible magnetic field and so designed that the microwave field rotation produced thereby is exactly 45. Generator energy passing through the rotator to the load and there reflected is returned to the receiver and not to the generator, the device thus serving as a duplexer. The phase relations in the load arms are either in phase equality or in. phase opposition depending upon the direction of the magnetic field in the rotator. The device is therefore a phase reverser, and both the duplexing and phase-reversing functions are performed by the same microwave field rotator simultaneously.

The magnetic. field may be generated by means of a coil, the circuit of which. can be reversed either by a mechanical switch or by connecting the coil to an alternating source having a square, sinusoidal or any other wave form. The invention thus provides a duplexer in combination with a phase reversing switch which may have no moving parts and which therefore maybe operated at high frequencies limited only by the distributed capacitance of the coil. Moreover, the switching device is distinguished from switches requiring moving parts in the microwave field space by the fact that this device presents constant impedance to the radio frequency power source during the switching operation.

One purpose of this invention is to combine the functions of a microwave duplexer' and a microwave switch in a single component.

, Another purpose is. to combine the functions of a microwave duplexer and a microwave phase-reversing switch in a single component.

Still another purpose is to. provide a microwave circuit containing. a switched field rotator of the magnetically energized type for simultaneous duplex transmission and reception, control of the microwave energy at dual outlets being governed by the switching of the field rotator.

A further understanding of this invention may be secured from the detailed description and drawings, in which:

Figure 1 depicts amicrowave guidev systemembodying theinvention.

Figure 2 depicts another embodiment of the invention including a phase-reversal switch integral with a duplexer.

Figure. 3 is a cross section of Fig. 2. taken on the line 3-3.

Figure 4 i'sa side view of Fig. 3, partlyinsection;

Figures Sand 6 schematically illustrate microwave'field distributions within the embodiment ofFig. 2.

United States Patent 'Guide 13' circuiting plate. The plate24 is. provided witha rectangular guide outlet 26, the round-to-rectangul'ar transition Patented May 5, 1959 Figure 7 depicts a modified form of the embodiment of Fig. 2.

Referring now' to Fig- 1,. a microwave generator 11 applies energy through a rectangular guide 12 to the end of a round guide 13. The transition between the rectangular guide 12 and the end of the round guide may comprise a quarter-wave transformer 16 as illustrated, or alternatively a tapered junction or any of. the other wellrecognized matching means for providing transition from rectangular to circular waveguide. The dominant TE mode of microwave transmission in rectangular guide 12 thus efiiciently excites the dominant TE mode in the round guide 13, the average direction of the lines of. electric force therein being parallel to those in guide 12.

A shunt rectangular side arm 17 is connected and matched to the round guide 13 with its axis at a distance from end 14, N being any integer including zero and a being the microwave length in guide. The axis of side arm 17 is in the described average TE field direction. These described locations of the connections of arms 12 and 17, together with the axial orientations of these arms, provide mutual isolation between them, so that a field in round guide 13 so oriented as to couplefully to one does not couple at all to the other. A. microwave receiver 18 is connected to guide 17.

The round guide 13 is connected beyond side arm 17 to a microwave field: rotator having an internal magnetizable rotating element such. as a ferrite element 15 and having a magnetizing coil. 19 concentric with the round guide 13. One formof such a device capable of rotating microwave energy inthe Faraday magneto-opti cal sense is described. in Patent No. 2,644,930,. of C. H. Luhrs et al.,, issued. July 7, 1.95.3. The two terminals 21, 21' of coil 19 are connected through a reversing switch 22 to a source of direct current represented by battery 23.

As is well known, certain forms ofv such rotators rotate the plane of polarization of microwave. energy passing therethrough by an amountproportional to the-magnitude of coil current, and the rotational sense isdependent upon the direction of current flow in thecoil, i. e;, the direction of magnetic. field, and is-independent of the direction of microwave energy flow, the direction. of rotation of the plane of polarization being described as clockwise or counterclockwise as seen by an observer at a. fixed location looking in the direction from the gentrator.

To illustrate, let it be assumed that when terminal 21 is positive, microwave energy passing through the rotator from left to right is rotated clockwise. It is an. experimental fact that when: microwave energy in transmitted from right to left it is likewise rotated clockwise, the observers position, of course, remaining fixed looking from left to right. When terminal 21' is positive, microwave energy passing from left to right is rotated counterclockwise and likewise rotated counterclockwise when transmitted from right to left. The amount of rotation is independent of the strength of the microwave-field- The rotator is connected to around guide. 13', which may be considered to be a continuation of guide 13.

is terminated. at the end 24 by a metal shortbeing matched in any desired way such as described for the transition between guides 12 and 13.. The-rectangular guide 26' is rotationally positioned at a 45 angle to guideIZ; so that microwave energy in the roundguide 13/13 can most efiiciently enter guide 26 onlyafter it has been given a clockwise rotation of45 Round guide 13 is also provided with an impedance matched shunt rectangular side arm 27 spaced from end 24 similarly to the spacing of arm 17 from end 14, that is, at a distance Side arm 27 is rotationally displaced from the median plane of the round guide taken through arm 17 so that, looking from the arm 17 at the left to arm 27 at the right, the position of the latter is displaced by 45 in a clockwise direction. The arms 26 and 27 are thus mutually isolated by their positions and orientations.

The output end guide 26 is connected to the shunt arm 28 of a magic tee 29, and the output side guide 27 is connected by a gradually curved guide 31 to the series arm 32 of the same magic tee 29. The other two arms of the magic tee, being the conjugate pair of collinear arms 33 and 34, are connected to non-reflective microwave loads of any form requiring selected relative phasing of the microwave energization. For example, these loads may consist of cooperating linear antenna arrays, depicted by arrays 36 and 37, the individual antennas or space radiators being of any type but here consisting of longitudinal slots in the broad faces of the arrays. In certain configurations of such cooperating arrays it is desired to operate the arrays with in-phase microwave energy tosecure one condition of operation, and to operate them with opposed-phase energy to secure another condition of operation. The arrays 36 and 37 are assumed to have such configuration in order to serve as an example of loading utilizing the output of the described microwave system.

In the operation of this device the current passed through coil 19 in either direction is of such strength as to rotate microwave energy passing through the rotator by 45 It is understood that the antenna arrays 36 and 37 are employed in some form of echo-generating apparatus so that echo energy received at the antenna is applied to the right end of round guide 13 and passes through the rotator from right to left. The generator 11 may generate either pulsed or continuous wave microwave energy, both being equally suitable for use with this invention.

The generated microwave energy is applied by rectangular guide 12 to the left end of round guide 13, setting up the TB field mode therein. The electric orientation of this mode being in the direction of the axis of side arm 17, no energy can enter this arm. The energy passes toward the right through the rotator, the switch 22 being in the position to make terminal 21 positive. Accordingly the field polarization is rotated 45 clockwise as it enters guide 13'. It therefore cannot enter side arm 27 but is properly polarized to enter end arm 26. It therefore is applied to the magic tee shunt arm 28 and excites the collinear arms 33 and 34 and their connected arrays 36 and 37 in the same phase.

Echo microwave energy returns to the arrays in phase, so excites the shunt arm 28 and not the series arm 32. The shunt arm 28 applies the echo energy through guide 26 to the round guide 13, exciting the TE mode therein. The microwave flow through the rotator being from right to left, the field is rotated clockwise, looking from left to right by 45 The energy therefore arrives at arm 17 at such orientation that it passes into the arm and to the receiver 18, and does not enter the end arm 12.

When the switch 22 is thrown to the position to make terminal 21' positive, energy applied from guide 12 is rotated counterclockwise by 45". This energy cannot then enter end guide 26 but is properly oriented to enter side arm 27, which it does, and enters the magic tee 29 through the series arm 32. The energy therefore excites the collinear arms 33 and 34 and arrays 36 and 37 in opposed phase. The echo of the antenna beam excites oppositely-phased microwave echo energy in antenna arrays. 36 and 37, so that the echo energy returns through guides 32 and 31 and not through guides 28 and 26. The re turning energy is rotated counterclockwise 45 by the rotator, so that it enters side arm 17 and not end arm 12.

During the travel time of switch 22, and in general during excitation of the rotator in any degree or sense, the impedance presented to the microwave field by the arms 26 and 27 remains constant, so that at no time is any discontinuity reflected from the arms during and due to the switching operation.

To recapitulate, the rotator serves as a duplexer, whichever way switch 22 is thrown, so that echo energy enters receiver 18 and not generator 11, while the positions of receiver arm 17 and generator arm 12 are such that generator energy from arm 12 cannot enter receiver arm 17 directly. Additionally, the microwave energizations of array loads 36 and 37 are either in phase or in opposed phase in accordance with the position of the direct-current direction-changing switch 22, which controls the rotator coil. The switched rotator in combination with the round guides 13 and 13' and their arms thus serves as both a duplexer and as a high speed constant impedance microwave switch having no moving microwave parts. The combination of these elements with a hybrid junction serves as a duplexer, as a constant impedance switch and as a phase reverser.

It is obvious that the above-described functions do not depend upon the type of switch 22 or upon its speed of operation. Therefore this switching function may be done by an electro-magnetic relay, an electrical squarewave or sinusoidal-wave dynamoelectric generator, an electronic oscillator, or by any other component applying reversing or alternating current to coil 19.

It is obvious that in place of the magic tee 29 any four arm hybrid junction having conjugate pairs of arms may be used. It is also obvious that in place of the end arm 12 and side arm 17 any two arms coupled to round guide 13 and electrically isolated for the T E mode may be employed. The same comment applies to arms 26 and 27.

It is also obvious in accordance with the above statement generalizing the characteristics of the output arms, that if the device he considered as terminated at arms 26 and 27, with any forms of microwave loads applied thereto, the application of the device is broadened because the switching function is no longer restricted to phase-reversing, but is a generalized microwave switcher comparable to a double-throw switch in wire circuits, and may be applied to any microwave switching use of this type.

A second form of the invention is depicted in Fig. 2 which dispenses with the hybrid junction 29, Fig. 1, but which nevertheless accomplishes the phase-reversing function performed thereby. f

Those parts which function similarly to parts of Fig. 1 are denoted by the same reference characters and include the microwave generator 11 which applies microwave energy to round guide 13, and the receiver 18 connected to round guide 13 through side arm 17. The rotator coil 19 is switched by switch 22 and the microwave field, after rotation, passes to the right into round guide ,13'. This guide 13' terminates in a conductive plate 24 forming a closed and short-circuited end. Two side arms 41 and 42 of the shunt type branch from round guide 13' at a distance of approximately from the closed end 24. These arms are connected to the round guide 13' at points which are angularly equidistant from a diametral longitudinal plane indicated in Fig. 3 by the center line 43 and are not diametrically opposite, their axial intersections with the round guide wall being less than apart. Arms 41 and 42 are depicted in Figs. 2 and 3 as collinear, but equal results will be attained by arms opening into the round guide 13 at the same locations but making any other desired angles therewith. The diametral longitudinal plane 43 makes an angle of 'eg-eeiaew 5 45 with diametral lqngitudinal'plane of roundiguide 13, Fig. ,2,v which comprehends the axes .of arms '12 and 17, this latter plane. being indicated 1 1 Kg. 3 y center line.4,4.

Inplace of the shunt arms 41 and 4. ,.1WSQFM S may be. employed: similar-1y. placed on round. guide,v 13 with similar results. I

Two coupling-matching vanes 46 and 47, Figs. 3. and 4, are provided, one in the plane 43, and the other in a plane perpendicular thereto. Thesevanes are preferably conductive, although they may alternatively be dielectric, and are. secured and joined to the end, plate 24-.v The coupling-matching properties of these vanes are. depend ent upon thevane length, breadth and.thickness,.aud.these dimensions are designed to produce equal coupling between the pair of arms 41 and 42 and the round guide 13 in the two transmitting field orientations, as will be described. later- It desirable, however, that each ot these vanes-be so. thin that the; vane. has: negligible ef c upon a microwave field having its average electric field direction perpendicular thereto. This requirement 18 generally satisfied if the metallic vane has a thickness of not over & inch at a frequency of 10,000 megacycles.

In order to provide an example of loading wh1ch requires the application of alternative inphase and antiphase microwave energy, two microwave antenna arrays 36 and 37 are schematically indicated as connected to the arms 41 and 42 by circuits schematically indicated at 48 and 49.

In the operation of this device, when switch 22 1s operated so that the terminal 21 is positive, the microwave field applied from generator 11 cannot enter side arm 17 (Fig. 2). The field is rotated 45 clockwise by the rotator and reaches the arms 41 and 42 with its average electric field direction at right angles to their common axis, which is the polarization most favorable for exciting them and the arms 41 and 42 are excited in phase. This action is illustrated in Fig. 5. The echo energy returned from antennas 36 and 37, Fig. 2, in phase reenters round guide 13 and is rotated clockwise 45 by the rotator, entering receiver 18.

When switch 22 is operated to make terminal 21 positive the generator energy is rotated counterclockwise, so that the average field direction at the arms 41 and 42 is oriented at 90 from its previous orientation, as indicated in Fig. 6. Since the microwave field distribution varies across the entrance to each of the side arms 41 and 42, each is coupled to the field and is excited. However, due to the direction of polarization of the TE field, these couplings are opposite in sense, with the result that the phases in the arms are in 180 opposition. The echo energy returned from antennas 36 and 37, Fig. 2, in antiphase relation reenters round guide 13' and excites therein a field oriented as indicated in Fig. 6. It is rotated counterclockwise by the rotator and enters receiver 18. Thus the two antennas 36 and 37, Fig. 2, are excited in the same phase or in opposed phase depending upon the position of switch 22. The impedance presented to the microwave field is constant during switching.

The coupling of arms 41 and 42 to round guide 13, as depicted in Figs. 3, 5 and 6, is near maximum for a field as indicated in Fig. 5, and consequently the coupling is near minimum for a field 90 thereto as indicated in Fig. 6. However, high coupling to a field as indicated in Fig. 6 is possible by appropriate impedance matching, and if equal excitation of the antennas in the inphase and antiphase senses is desired, these couplings must be made equal. This may be done in either of two ways or by a combination of them. The two arms 41 and 42 may be changed in their positions on the round guide by being moved toward or away from each other until the couplings are equal, or end vanes 46 and 47 may be employed. It is evident that vane 47, Fig. 5, has no effect at the entrances of the upon theindicated-field butthe vane 46 does have', and

that the latter, by modifying the field configuration, controls thecoupling of arms 41 and 42 to a field so oriented; I-t also evidentthat vane 46', Fig. 6, has no effectupon' that field but that vane 47" does. Thus the two vanes ind'ependently affect the arm couplings in the two field orientations, so that by appropriate design or thesevanes the couplings may be independently adjusted to be equal.

The output guide arms of Fig. 3 maybe disposed in a slightlydifierent manner, asd'epicted in Fig, 7, yet Will operate the same. If it be considered. that the arm 41', Fig; 3; be transferred to; a position 180 displaced from that shown; it will then occupy the position of 41", Fig, 7, adjacent to arm 42 but on the opposite side of the diametral? plane D D from it: ()bviously such a change will not. afiect operation either ina field oriented as in Fig. 5 or'in' one-perpendicular thereto as in Fig. 6, or in a field at any'interme'diate orientation. However, due to the inclusion of" the elbows in Fig. 7, the field direct-ions as'indicated' by arrows 48"and 49 at the exits of arms 42 and 41' have opposite directions relative to each other, differing from arrow directions 51 and 52 guides for the field of Fig. 5. Similarly, when the field is oriented as in Fig. 6 the graphic indication of output phase in Fig. 7 difiers from that of Fig. 6 merely because of the inclusion of the elbows.

To recapitulate, a single microwave rotator serves simultaneously in three capacities: as a duplexer, as a mi crowave switch presenting constant impedance during switching and having no moving parts within the microwave field and which may be operated at high speed, and as a microwave phase reverser.

What is claimed is:

1. A microwave duplexer and comprising, a round waveguide section, a pair of mutually isolated arms connected to one end thereof, a microwave energy source connected to one arm of said pair of arms propagating a microwave field in the TB mode in said round waveguide, a microwave receiver connected to the other of said pair of arms, a second pair of arms connected to the other end of said round waveguide section, microwave field rotating means active in the Faraday magneto-optical sense positioned in said round waveguide section intermediate said pairs of arms, means for impressing a magnetic field on said field rotating means, said magnetic field having a magnitude sufficient to cause said field rotating means to rotate the TE microwave field by an angle of 45 in a direction dependent on the direction of said magnetic field, means for periodically reversing said field, and means including said second pair of arms for securing a pair of microwave outputs of phase equality or opposition dependent on the polarization of the microwave field at said second pair of arms.

2. A microwave duplexer and switch adapted to be energized by a microwave field comprising, a round waveguide section having a first pair of mutually isolated arms connected to one end thereof, a second pair of mutually isolated arms connected to the other end thereof, said second pair of arms being displaced 45 as re spects said first pair of arms, microwave field rotating means active in the Faraday magnetooptical sense positioned in said round waveguide section intermediate said first and second pair of arms, means for impressing a magnetic field of such intensity on said field rotating means as to rotate said microwave field by an angle of 45 in a direction dependent on the direction of said magnetic field, means for periodically reversing said field, and a hybrid microwave four-arm junction having the respective arms of one conjugate pair of arms thereof connected to respective arms of said second pair of mutually isolated arms and the respective arms of the phase-reversing switch comprising, a round microwave guide having a first pair .ofrnutually isolated armsconnected to one end thereof,

a microwave source connected to one arm of said first pair of arms propagating a microwave field in the TB mode in said round guide, a microwave receiver connected to the other arm of said first pair of arms, a second pair of mutually isolated arms connected to the other end of said round guide having an orientation differing by 45 from the orientation of said first pair of arms, an electromagnetically energized microwave field rotator in said round guide intermediate said two pairs of arms, said rotator being energized by a reversible direction current supply source of a magnitude such that the TB micro wave field in said round guide is rotated thereby by 45 in a sense dependent upon the direction of said current,

and a hybrid microwave four-arm junction having the respective arms of one conjugate pair of arms thereof connected to the respective arms of second pair of mutually isolated arms, whereby energy applied at one arm of said first pair of mutually isolated arms when reflected and returned through said hybrid junction goes to said receiver, said rotator causing said source and said receiver to operate in duplex, and whereby the microwave energy from said source is emitted from the other conjugate pair of arms of said hybrid junction in equal or opposed phase depending upon the polarization of said TE microwave field.

References Cited in the file of this patent UNITED STATES PATENTS 

